Toroidal continuously variable transmissions are used in automobile transmissions, or as transmissions for adjusting the operating speeds of various kinds of industrial machinery such as pumps. Continuously variable transmissions having a wide transmission gear ratio that is increased by combining a toroidal continuously variable transmission with a planetary-gear transmission have also been proposed.
FIG. 18 to FIG. 21 illustrate an example of a continuously variable transmission apparatus that is formed by combining a toroidal continuously variable transmission and planetary-gear transmission as disclosed in JP 2004-084712 (A). This continuously variable transmission apparatus is formed by combining a toroidal continuously variable transmission unit 1 that is the toroidal continuously variable transmission and a planetary-gear transmission 2 that is a differential gear unit that includes a 3-step unit having an initial step, middle step and final step, by way of a low-speed clutch 3 and a high-speed clutch 4. By switching the connected and disconnected states of the low-speed clutch 3 and the high-speed clutch 4, and by adjusting the transmission-gear ratio of the toroidal continuously variable transmission unit 1, it is possible to infinitely adjust the transmission-gear ratio between the rotating input shaft 5 and output shaft 6. In other words, by adjusting the transmission-gear ratio of the toroidal continuously variable transmission unit 1 in the low-speed mode, which is a state in which the low-speed clutch 3 is connected and the high-speed clutch 4 is disconnected, the output shaft 6 is able to be rotated in both directions from the stopped state, while the input shaft 5 continues to rotate in one direction. On the other hand, in the high-speed mode, which is a state in which the high-speed clutch 4 is connected and the low-speed clutch 3 is disconnected, as the transmission-gear ratio of the toroidal continuously variable transmission unit 1 is changed toward the side of increased speed, it is also possible to change the transmission-gear ratio of the entire continuously variable transmission apparatus toward the side of increased speed.
This kind of toroidal continuously variable transmission unit 1 includes: a pair of input disks 7a, 7b, which is a pair of outside disks; a single integrated output disk 8, which is an inside disk; and plural power rollers 9. The pair of input disks 7a, 7b are arranged so as to be concentric with each other by way of an input shaft 5, and so as to be able to freely rotate in synchronization with each other. The output disk 8 is arranged between the pair of input disks 7a, 7b so as to be concentric with the input disks 7a, 7b, and so as to be able to rotate relative to the input disks 7a, 7b. The power rollers 9 are held in the axial direction respectively between both side surfaces in the axial direction of the output disk 8 and one side surfaces in the axial direction of the input disks 7a, 7b. The power rollers 9 rotate with the rotation of the input disks 7a, 7b, and transmit power from the input disks 7a, 7b to the output disk 8. In this specification, the “axial direction”, unless stated otherwise, is the axial direction of the input disks and output disk.
The output disk 8 is rotatably supported by a pair of rolling bearings such as a pair of ball bearings 10, which are thrust angular bearings on both end sections in the axial direction thereof. The power rollers 9 are rotatably supported respectively by the inner side surfaces of corresponding trunnions 11, which are support members. A pair of support plates 12a, 12b for supporting both end sections of the trunnion 11 are provided on the inside of a casing 13 by way of an actuator body 14, a connecting plate 15 and a pair of support columns 16. The support columns 16 are respectively constructed by mutually connecting support-post sections 17a, 17b that are provided on opposite sides in the radial direction of the input shaft 5 so as to be concentric with each other, the outer-circumferential surfaces of which are spherical convex surfaces, by a support-ring section 18 having a circular through hole 18a. The input shaft 5 is inserted through the inside of the through holes 18a of the support-ring sections 18.
The bottom end sections of the support columns 16 are positioned on the top surface of the actuator body 14 by uneven engagement, and joined and fastened by bolts 19. In other words, the rod sections 20 of the bolts 19 are inserted through through holes 23 that are formed in a lid body 21 and through holes 24 that are formed in a main body 22 of the actuator body 14, and the tip-end sections of the bolts 19 protrude from the top surface of the main body 22. The tip-end sections of the bolts 19 are screwed into screw holes 25 that are formed so as to be open on the bottom surfaces of the bottom sections of the support columns 16 (portions that include support-post sections 17a), and further tightened to join and fasten the bottom end sections of the support columns 16 to the actuator body 14. By firmly fitting the bottom end sections of the support columns 16 on the top surface of actuator body 14 in concave engagement sections 26 that are formed so as to surround the top-end openings of the through holes 24 of the main body 22 so that there is no looseness, it is possible to position the support columns 16 with respect to the actuator body 14. On the other hand, the top-end sections of the support columns 16 are joined and fastened to the bottom surface of a connecting plate 15 that is fastened on the inside of the casing 13 by bolts 27, the installation position thereof being regulated by uneven engagement. In other words, the rod sections 28 of the bolts 27 are inserted through through holes 29 that are formed in the connecting plate 15, and the tip-end sections of the bolts 27 protrude from the bottom surface of the connecting plate 15. The tip-end sections of the bolts 27 screw into screw holes 30 that are formed so as to be open on the top surfaces of the top end sections of the support columns 16 (portions that include the support-post sections 17b on the top side), and then further tightened to join and fasten the top end sections of the support columns 16 to the connecting plate 15. In this way, the pair of support columns 16 are provided so as to span between the top surface of the actuator body 14 and the bottom surface of the connecting plate 15. Support holes 31a that are formed in the support plate 12a on the bottom side fit around the outside of the support-post sections 17a on the bottom side of the support columns 16 so that there is no looseness. Moreover, support holes 31b that are formed in the support plate 12b on the top side fit around the outside of the support-post sections 17b on the top side of the support columns 16 so that there is no looseness.
The actuator body 14 is the portion that houses the main-unit section of the actuators (not illustrated in the figures) for causing the trunnions 11 to displace in the axial direction of the rolling shafts 11a that are provided on both end sections of the trunnions 11, and is fastened to the bottom section of the casing 13. In order for this, a stepped section 32 is formed in the portion near the opening on the bottom end of the inner surface of the casing 13, and bolt-insertion holes 33 (see FIG. 21) are formed in the portions near both ends in the width direction (front-back direction in FIG. 18 and FIG. 19, and left-right direction in FIG. 20) of the actuator body 14. When fastening the actuator body 14 to the inside of the casing 13, the portions near both ends in the width direction of the top surface of the actuator body 14 come in contact with the stepped section 32. Then, bolts (not illustrated in the figure) are inserted through the bolt-insertion holes 33 from the bottom and screwed into screw holes that are opened in the stepped section 32, and further tightened. On the other hand, the connecting plate 15 is located on the top-end section of the inside of the casing 13 with the position in the length direction (left-right direction in FIG. 18 and FIG. 19, and front-back direction in FIG. 20) and width direction being regulated. In order for this, a positioning sleeve 35 spans between the top surface of the connecting plate 15 and the bottom surface of the top-plate section 34 of the casing 13. Both end sections in the axial direction of the output disk 8 are rotatably supported by ball bearings 10 in the support-ring sections 18, which are provided in the middle section of the pair of support columns 16 that are fastened in a specified position inside the casing 13.
In this kind of continuously variable transmission apparatus, making the support rigidity in the axial direction of the pair of support columns 16 with respect to the actuator body 14 and connecting plate 15 as high as possible is desirable. In other words, during operation, forces in opposing directions that are applied from the pair of input disks 7a, 7b to the both side surfaces in the axial direction of the output disk 8 by way of the power rollers 9 cancel each other out inside the output disk 8 when the torques that are transmitted to the output disk 8 from both input disks 7a, 7b are equal. However, when friction loss occurs in the planetary-gear transmission 2 that is provided on the outside in the axial direction of one input disk 7b of the pair of input disks 7a, 7b, and it is not possible to balance the forces in opposing directions that are applied to the both side surfaces in the axial direction of the output disk 8, a force in the axial direction (thrust load) is applied to the middle section of the pair of support columns 16 that rotatably support the output disk 8.
In this conventional construction, by connecting the base-end section (left-end section in FIG. 18) of a hollow rotating shaft 41 with the output disk 8 with a spline engagement, and inserting the hollow rotating shaft 41 through one of the input disks 7b of the pair of input disks 7a, 7b so as to be able to rotate freely, it is possible to obtain the rotating force of the output disk 8. On the other hand, as illustrated in FIG. 22, it is also possible to integrally form an output gear 42 around the outer-circumferential edge section of the output disk 8a, and to obtain the rotation of the output disk 8a by way of the output gear 42. In the example illustrated in FIG. 22, the output gear 42 is a helical gear for the purpose of reducing vibration and noise that occurs when transmitting power. Therefore, when transmitting power, a force in the axial direction (thrust force) is applied to the output disk 8a, and this force in the axial direction is applied to the pair of support columns 16 by way of ball bearings 10 (see FIG. 18 and FIG. 19) that rotatably support both end sections in the axial direction of the output disk 8a. 
In this way, making the support rigidity in the axial direction of the pair of support columns 16 high is desirable, and as a method for doing so, increasing the shaft diameter of the bolts for supporting the bottom end sections of the support columns 16 with respect to the actuator body 14, and increasing the shaft diameter of the bolts 27 for supporting the top end sections of the support columns 16 with respect to the connecting plate 15 is feasible. However, when the shaft diameters of the bolts 19, 27 are increased, there is a possibility that the size and weight of the continuously variable transmission apparatus will be increased, and that the head sections of these bolts 19, 27 will protrude from the bottom surface of the actuator body 14 or from the top surface of the connecting plate 15.
Even in a state in which the rod sections 20, 28 of the bolts 19, 27 are screwed into screw holes 25, 30 and further tightened, minute gaps exist between the male-screw sections that are formed around the outer-circumferential surfaces of the rod sections 20, 28 and the female-screw sections that are formed around the inner-circumferential surfaces of the screw holes 25, 30. The screw holes 25, 30 are provided in the radial direction of the input disks 7a, 7b and output disk 8, which is a direction orthogonal to the axial direction. Therefore, when a force is applied in the axial direction to the support columns 16, there is a possibility, even though small, for the support columns 16 to rotate (to become loose) around the center axes thereof due to the existence of the minute gaps. When the support columns 16 become loose, the parallelism between the pair of race rings of the ball bearings 10 that are provided between both end sections in the axial direction of the support columns 16 and output disk 8 is impaired. Therefore, edge load is applied to the rolling contact areas between the race surfaces of the ball bearings 10 and the rolling bodies, and there is a possibility that durability of the ball bearings 10 and the toroidal continuously variable transmission unit 1 will decrease. In order to prevent this kind of rotation of the support columns 16, together with supporting and connecting the pair of support columns 16 to the actuator body 14 and connecting plate 15 by the bolts 19, 27, spanning rotation-prevention pins between the support columns 16 and the actuator body 14 and connecting plate 15, or forming a flat surface section that comes in contact with these is feasible. However, in that case, the manufacturing cost of the continuously variable transmission apparatus increases.